Shock testing device



July 19, 1949. E. R. HARRlS SHOCK TESTING DEVICE 2 sheetssheet 1 FiledJan. 14, 1946 or m EDWARD R. HARRIS AT TO RNEY July 19, 1949. E. R.HARRIS SHOCK TESTING DEVICE F iled Jan. 14, 1946 2 Sheets-Sheet 2 .d uw

FIG.

FIG. 4.

INVENTOR. v EDWARD R. HARRKS ATTORNEY Patented July 19, 1949 SHOCKTESTING DEVICE":

EdwardR'. Harris; Los Ang'eles; CalifLa'ssig'niiij to th'e-UnitedStatesof America as re resented-by the Secretaryof Wur Application January 14,1946; Scrial-No.'6 1-1,1-54i 8 Claims.- (G1. 315*364') (Grantedunder theact of--Ma1"ch-3, 18833223 amended April 3 0, 1928; 370" O; "757i" Theinvention described herein may b'e'manufactured and used by or fortheGovernment for governmental purposes, without the payment- 0 me of anyroyalty thereon.

The present inventionrelates to improvements in shock testing devices-JIn connection With"thebui1din'g.:oi electronic equipment, particularlyfor Y military usage; a number of testing devices have been-evolved-todetect mechanical weaknesses, arid-to facilitate their elimination,- sothat the equipment and its components will withstand the-:various joltsand the rough handling which'it is likelyto receive in use. It isparticularly importanct to test vacuum tubes in this respect; However;testing devices which have cometoap plicants attention have not beenentirely-satisfactory. 7

Among other things, test impactsshould 'be directed at the base of the"vacuum tube-rather than at its glass envelope; Thisprocdureis believedto be correct becauseinactual use atube sustains all or most of itsshocks through the chassis of the equipment and the tube b'aseratherthan through the tube envelope. Also a:bl0w upon the glass env'elopeisnot a satisfactory test as glass envelopes are more prone to -vary: inthickness and strength than-themoreuimportant components of a tube andhencethe'results of tests I involving a Y blow on the glass envelopearenot truly indicative of theability of the tube to withstand shocks.Again; shock'testingcde vices should preferably incorporatesome"quantitative means to determine and standardize tne amount of shockbeing'imparted' Also as the type of shocks which have been foundto'be'm'ost destructive to vacuum tubes have a sharply-peaked curve ofvibration, this type of shock sho'uldxbe most closely simulated intesting devices. In devices which utilize heavy'hammer m'eanspthe curveof vibration-of the impact imparted has a rounded peak, clue" totherelativelygr'eat inertia of such'hammermeansi- It is thereforea'principlelob'ject-of the present invention to provide apparatus todetermineiithe extent to which electrontub'es can stand-rough handlingand use;- before observable 7 changes o'c cur in the electricaland/ormechanical charac'- teristics thereof.

It is anotherobject to provide means of adequately measuring the impactforce impa'rted to an electron tube so that the testing procedures maymore readilybe standardized;

It is-another objeet to provideta' bumpr test device whereby a"- blewmayfv be delivered from the-same angle a'nd strike the same placeteachtime it is desired? 7 It is anotherobject to prlfliid a bump testerwhich iriipart tothe base 'rather than to thee'nvelop Ta tube;

It is a -further object to" provide an impact test devicewhich can maketests with a tube in an 'up'rig'htorin aninverted position; and in'which a tube may: be:rotated 'about its' axis sa es" to receive blowsfrom -difi'ereiit directions as may be deeme'd advisablei I It' is stillanother'object-"te provide an ii-r'ipact test device which is relativelysimple and inexpensive-to manufactureand' which is compact in size'aridea'sy te operatl It is yet anotherobject to pr'ovide a bump tester whichrfla'yb'emeaunyoperated: by a p'e'rson with no previous 'skfll,

Itis still-a further object tb provide a bump tester which requiresmoeasi-1yupset criticalad ustments; which is sturdy and portable; andwhich maybe simply cenipeh'satedfor variations due to the eleriie'ntsand-the age and condition of the parts.

Itisalso an object 'toprovidean impact-test device whichis adapted toclosely re-enact the types of shock encount'ered' in actual use,-includmg the vibratory-- components or: gun fire or ballisticexplosions.

It -is-a further object -te provide a bump tester whereby any" selectedht'hiriiefblbtv may be duplicated and the force: of 1 the impact thereofmay be registered in comparativeunitswhich may be calibrated andeasily-expressedin footpoundsor gravity units.

It is' still anothei' 'object teprovide a-mech'anisrn fo'r determinin tuggedness and ability of an" elfct'rohic' ti-i ithsta'I-fd 1 rough"usage by" reproducing an co" reliably exaggerating the componentsdestruc'tlv to riorm al tube-' life, and" Ineasuringthem gravity orother suitable units It isa further-object to provide an irnpact' testdevice whereby ti -1eweak poin ts' of' a tilbe may be localized so thatinfermative' data-may be acquired relatii e to improvement of 5thetl'l'bel- These} and other objbts' and-advantages 0f my I presentinvention, will be -better understood. astne cetan c dscrlptien thereof"progresses, are obtainedin the feliowing-manrier:

I provide an impact-*tesfi'devi'ce which incorporates an elongatedharnm-er at relatively light weight; which is: canner /mounted atitsproximal end to a basetahdi's provided-with an adjustable spring meansby which the-speed of its stroke mawbe varieam Positiciieli' sfi a'sitdbe" etern ty th'e distal end-o'r the na'nimer is an anrwnienisesteemed to the base that it will respond vibrationally to a hammerstroke. Said anvil sustains one of several interchangeable tube sockets,which are of different sizes and shapes so as to accommodate differenttypes of vacuum tubes, and provision is made for eifecting electricalconnections with a tube without any undue strain on its terminal prongs.The anvil is preferably rotatable so that it may be struck on diiferentsides and the tube sockets are rotatable relative to the anvil, so that,by rotating the anvil and socket, a tube may Joe struck from everypossible angle.

The amount of swing of the hammer is controlled by a ratchet memberwhich is adapted to hold the hammer at any one of a plurality ofpositions, angularly spaced from the anvil, and to release the hammerand allow it to freely swing toward the anvil under the urging of thespring means. Thus, by adjusting the spring tension on the hammer andadjusting the position from which the hammer is released for its stroketoward the anvil, a multiplicity of impacts of different forces andcharacteristics can be obtained.

There is also provided an impact measuring member by which the force ofan impact can be determined so that, despite changes in the tension ofthe spring with time, temperature and other factors, a standard range ofimpacts can always be duplicated. Said impact member includes a pendulumand a scale and a pointer to indicate the maximum amount swing impartedto the pendulum when struck by the hammer. To determine the force of anin pact to which a tube is subjected, the said impact measuring memberis positioned upon the base in a position to receive the hammer biow inplace of the anvil. When the hammer is released, it strikes the bob ofthe pendulum and causes it to swing and the pointer indicates themaximum point of its swing. The scale may be calibrated in any suitableunits.

In the accompanying specification there is d scribed, and in the annexeddrawings shown, what is at present considered a preferred embodiment ofmy present invention. It is however to be understood that said inventionis not to be limited to said embodiment, inasmuch as changes therein maybe made without the exercise of invention and within the true spirit ofthe claims hereto appended.

In the drawings,

Figure 1 is a perspective view of a preferred form of shock testingdevice embodying the present invention, shown with a vacuum tube inposition, the parts being shown, before release of the hammer, in solidlines and, after impact with the anvil, in broken lines;

Figure 2 is an elevational view or the impact measuring member usablewith said device, the pointer being shown in an indicating position;

Figure 3 is an elevational view taken along the line 33 of Figure 2, theimpact measuring dcvice being shown in position upon the baseboard,which is shown in section, and the pointer being shown in its zeroposition;

Figure 4 is an enlarged elevational view, partly sectioned, of the tubesocket of Figure 1;

Figure 5 is a plan view, partly broken away and sectioned, of Figure 4;v

Figure 6 is an enlarged sectional view partly in elevation of the anvilin position in the baseboard; and

Figure 7 is a plan view of Figure Referring now more particularly to thedrawings, there is shown a preferred embodiment of the presentinvention. It comprises a fiat, horizontally disposed, baseboard H, ofplywood or other suitable material. Pivotally secured to said baseboardH, by means of a vertically disposed hammer pivot pin I3, is anelongated hammer :5 (Figure l). A coil spring ll, wound around the pivotpin G3, has its upper end secured to the hammer i5 and its lower end toa tension adjusting plate l9.

Said plate I9 is a circular disc of metal provided with a center hole toaccommodate the said pivot pin (3 and a plurality of spring holes 2|about its peripheral portion. Said spring holes 21 are receivable to ascrew 23 which extends down into the baseboard H to secure the plate 19against rotation. The hammer [5, which urged by the spring l'l intoclockwise rotation about the pivot pin I3, has a contact head preferablyof hardened steel, secured to one side of its distal end and it is alsoprovided with 2. depending ratchet pin 27, a depending pointer finger 29and an upwardly extending hammer handle 39. Scale markings 32 aredisposed an arc upon the baseboard II so as to cooperate with thepointer finger 29.

Also pivotally secured to the baseboard ii, by means of a ratchet pivotpedestal 35, is an arcu ately-shaped ratchet member 3i (Figure 1), whichis provided, at its outer end, with an up wardly extending ratchethandle 8? and, along its inner edge, with a plurality of notches 3treceivable to the ratchet pin 21 aforementioned. The shape of theratchet member 31 should be such that when it is swung away from theratchet pin 21, so as to disengage it, the hammer i5 is free to swing tothe anvil 49 described below, without the possibility of said pin 2?coming into contact with said ratchet member 3i. This may beaccomplished by making the radius of the ratchet member 3| equal to thedistance between the hammer pivot pin 83 and the ratchet pin 27 and bypositioning the ratchet pivot pedestal 35 at a slightly greater distancefrom said pivot pin [3. A ratchet stop 39 is also secured to thebaseboard H so as to limit the outward swing of the ratchet member 3!.

The baseboard II is also provided with a circular aperture 41 (Figures 3and 6) which is provided at its lower end with a sleeve 63, preferablyof bronze, and above said sleeve with a resilient collar 45, preferablyof soft rubber. The inner surface of said sleeve is preferably taperedat both ends so as to form a substantially single circular line 46 atits smallest diameter. Said sleeve 43 and collar 45 are coaxiallydisposed and are receivable to a cylindrical shank It? of an anvil 49(Figures 1, 6 and 7), the said line 58 making a fairly snug fit aboutthe lower end of said shank but still allowing said shank to berotatable and also allowing said anvil a certain amount of freedom tooscillate laterally at its upper end. The upper end of said shank t? isencircled by a loosely fitting fiat metal washer 50. Said anvil 49 ispreferably made of hardened steel and is provided near its upper endwith four flat vertically disposed anvil surfaces 5i, and its upper endis hollowed out so as to be snugly receivable to a cylindrical shaft 53of a tube socket 55.

The tube socket 55 (Figures 1, 4 and 5) is made up of a hollow metal cup57 secured coaxially to the upper end of said shaft 53. The cylindricalwall of said cup 51 is pierced by a plurality of openings 59 and itsinner surface is cut by a vertically disposed slot 6|. In the drawingsfour such openings 59' areshown 'as the tube S0016t-f55 is adapted totake "a vacuum tube '62 havingbut four terminal pronga 'butotherinterchangeable tube sockets to I take other -tubes *should also beprovided. The upper portion of said cup 51 is also provided with twothumb-screws 63 positioned approximately perpendicularto each other andextending through thewall of saidcup.

A tube adaptor 65* (Figures 4 and '5) is positioned within thecupfil."Saida'daptor 65 is a hollow shallow cylindrical '--member, of suitableinsulating material and its upper wall -is pierced bya plurality ofprong holes itl' wfourbeing shown in the drawings), receivable-Watime-*terminal be tested. Said adaptor 65fis securedtothebase of the cup51 by means of a- 'bolt iiilwhl'ch-is loose enough to leavethe-adaptorfreeto retatawith in said cup.-

Sustainedwithin the hcllowadaptor 65, by v means of bolts ll, arefeurcontact elements 13, of fiat sprin'gymetal, which-contact elementsrespectively'are maintained in arcuatepositions by means of fourterminal-screws: Said ter minal screws '15 are "threaded: horizontallythrough the-walls of-saidadaptorth and extend through the-openings 59;Each of 'said terminal screws i5 is encircled by a ring l8 ofinsulatingmaterial, to insulate 'it from the cup 5?. Said terminal screws'15:arearecessed circumferentially near their heads so as to-..be-.receivable to conventional alligator .ztype electrical contactclips (notishown), or-other suitable connective means.

Intermediate the icircular..=aperture x ii, 'mentioned above, andthe-hammerpivotpin 13; there is secured to :the baseboardhl I a'rrubber"covered fender 16 (Figures :1; and i3) :adaptedsto stop :the swing ofthe hammer 1.5 ':when :its -.ir'npact is be= in measured, as will.become;clear,-hereinafter.

A metal ferrulefll (Figure 3) is secured through a hole in thebaseboardill;.ju-st;beyondthe circular aperture-M.Said=ferrulev11supports an impact measuringdevice Newhichds made up of avertically disposed" standard: 8!; terminating at its lower end-in a.cyli-ndricalplu .83 which makes a snug-fit'in'the said ferru1e-:'II.Acircular scale 85, marked ofi in foot-pennds a or-other suitablecalibrations and extending; through about. 90, and a short; horizontal.pin -.81 are fastened.- to the front of the standardIApendI-Ilum-piVotshaft B9 extendsthrough.thenpper;end-oi the standard8| and.is-prevented from rotating by a set screw 90. Pivotally suspendedfrorn-;.said shaft 89 are a pendulum 9l, ;w -hich-,is .freeto, swingthereabout, and v a 5 pointer- -;93, -whichis. maintained in lightfrictional engagement ;-withthe standard BI- by means of-a-springvwashert l, so that itpivots thereabout only so farras-dt .isactually pushed.

The pendulum Si is provided with a bob 95, preferablyofhardenedsteelrand a rearwardly extendingfinger ill. The pin 81mentioned above 'andthe finger 9! are so positionedjthat,said pin actsas a stop for the pointer 93' when in its zero position and the fingerengages the 3 said pointer and pushes it upwardly along the scale 8 5.when the pendulum 9| is caused toswing in acounterclockwise direction.

In the operation "of the impact testingdevice .7

just described, an electronic tube 62 may be tested as follows: theimpact measuring member 79 is placed in operating position upon thebaseboard H by inserting the plug 83 into the ferrule '51, the scale 85being placed so as to extendaway from the hammer- I 5.- Thabob-QE is imer-i lfi swings in a clockwiseudirection and strikes-the bob I causinitnto swing upwardly in a counterclockwise direction. and: carry thepointer 93 along with. it. The xbobntizswings back :but the pointer 83is frictionallyr, retained, bysthe spring was'her 94; at thei'highestxpointof the pendulum swing, thus indicating, upon-the'scale-85,ithe.f0rce of-theimeact of thewhammer i=5.'Saidimpact-forcesmay be increased orzdecreased .by releasingvtheshanurner 1S5: from "differentnotches 33, or-ithe; tension of thespring 'Himay .be varied byeremoving the screw 23': and

rotatin the ,tension :a'djusting plate 1 9': ts an-- other-position.

:W-hen -.-a suitable force "orzimpact has been obtained, the: impact"measuring member 39- is.:re-

:moved entirely- Ffrom the baseboard" l l "and the anvilwdS is securedthereto *by inserting. its 'cylindricalt'shankel down-:into therubberzcollar 45 .and the :metahsleevei43. vAtuilie :socket 55, of .asize to accommodate-a ;p articular electronic tube b2-v to be tested, isthen-goperationally positioned by. inserting itsshaft 53-;into theupper-en'd-of the anvil 49.

The tube 62 is then insertedyinto' the. tube socket 55, the terminalprongsrthereofgextendingthrough the :prengholes fil and ;the tube beingsecured within saidsocket by'meansof thethumb screws 63, The,terminaLscrews l5 arexthen screwed inwardly until the contactelements13 ;:make electrical connection with the terminal prongs of :the tube B2Electrical con- 1 nection between the; tube; ;62 and ,an outside circuit1 may then tie-effected by means: of alligator type; clipssnapped on to1 the; outer .-en;dsof the terminal screws l5; In-view of i the .factthat in tubes havin a bayonet pin on-;the1-side;,of its base, the pin:is not always 2 in exactly the same position relativete theterminal-prongsthereof, the; tube v adaptqifrfi is rotatablesuiiicientl-y to allow difierent tubes to beepq itioned in the tubesocket-.55. The terminal screws l5;;-are free .to move with the adaptorG5 in View oil-the relatively large openings 59throughiwhich.they-extend.

The hammeri-5.-is tlqien caused to strike. the anvilAQ thus transmittingthe shock,to.;the electronic tube .62. The tube tamays-be struck, fromextent. about vits lower end. The;.rubber collar 15 provides the upperend of the anvil 49;.W 1ihasufli- .cient lateral freedom sothat-itecansuitably oscile at s sie r nsm c iscilla i ns 1 0- e ubsocket 55 and tube 62. The result is that, the pivot point being at thelower end of the anvil 49, said parts form a mechanical amplifier sothat the tube 62 receives lateral deflections of greater amplitude thanthe anvil.

ordinarily occurs in actual practice.

Although the hammer I5 is relatively light in weight, by suitablyadjusting the angular distance of its swing and the tension on the sprinll, it is able to impart an impact of sufiicient force, as it strikes athigh speed. The relatively small mass of said hammer 15 however haslittle inertia and thus there results a sharp peaked curve of vibration,unlike the rounded peaked vibration curve which results when a heavierhammer is used.

The device described above simulates actual operating conditions in thatimpacts are transmitted to a tube through its base which is what Alsothe type of shock produced, as already described above, is similar tothe type to which a tube is most generally subjected under operatingconditions, and particularly the type sustained by a tube when subjectedto ballistic explosions when in military use.

Electrical connections are provided so that the tube may be coupled to asuitable electrical circuit while it is being tested so thatfluctuations in current will indicate variations in interelectrodespacing of the tube as a result of the mechanical impacts. It will beseen that the terminal screws 15 are purposely of small diameter and arenot knurled so that excessive pressure on the terminal prongs and injurythereto are prevented.

While there has been described what is at present considered a preferredembodiment of the invention, it will be obvious to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the invention, and it is therefore aimed in the ap- :1

pended claims, to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What is claimed is:

1. In a shock testing device for an electron tube, u

an anvil, socket means sustained by said anvil and receivable to thebase of said tube, a hammer, adjustable means to cause said hammer tostrike said anvil, means adapted to measure the force of impactimpartable by the hammer to the anvil.

2. In a shock testing device, a hammer, an anvil, adjustable means toactuate the hammer to cause it to strike the anvil, the anvil beingpivotably sustained so as to be oscillatable when struck by the hammer.

3. In a shock testin device as defined in claim 2, the anvil beingpivotably sustained by means of a sleeve providing substantially linecontact about said anvil near one end thereof, and a collar of resilientmaterial substantially surrounding said anvil.

4. In a shock testing device, a hammer pivotably sustained at one end,spring means adapted to urge said hammer to swing in one direction aboutits pivot, an arcuate ratchet member adapted to releasably hold saidhammer against such swinging movement, scale means to indicate theangular position of said hammer when held by said ratchet means.

5. In a shock testing device as defined in claim 4, means adapted tomeasure the force of impact which may be imparted by the hammer when itit released.

6. In a shock testing device of the type having a hammer, means adaptedto measure the impact 7 which the hammer may impart, said meansincluding a pendulum adapted to be struck by the hammer and means toindicate the maximum swing of the pendulum resulting therefrom.

7. In a shock testing device for an electron tube, a baseboard, arelatively light weight elongated hammer pivotably mounted thereon,spring means to impart a relatively high speed swing to said hammer, avertically disposed elongated anvil secured to said baseboard so thatits lower end is substantially held against lateral movement while itsupper end is able to oscillate pivotably about said lower end, resilientmeans to limit the amount of such pivotable oscillation, rotatablesocket means sustained by said anvil and receivable to an electron tube,means to releasably hold said hammer at any one of a plurality ofpositions at different angular distances from said anvil, said lastnamed means including a ratchet member pivoted to said baseboard and aratchet pin secured to said hammer and cooperable with said ratchetmember, means to measure the impact impartable by said hammer to saidtube, said last mentioned means including a pendulum positionable to bestruck by said hammer and indicating means to show the maximum swingimparted to said pendulum when struck by said hammer.

is. In a shock testing device for an electron tube having downwardlyextending terminal prongs, the combination including an anvil, socketmeans sustained by said anvil and receivable to the base and terminalsof said tube, a hammer, adjustable means to cause said hammer to strikesaid anvil, and means adapted to measure the force of im pact impartableby the hammer to the anvil, said socket means including a cylindricalcup provided with a vertical slot on its inner surface and a plu ralityof openings through the wall thereof, a shallow cylindrical tube adaptorrotationally po sitioned in the base of said cup, said adaptor including a top wall and a tubular lateral wall of insulating material andhaving a central cavity within said lateral wall and being provided witha plurality of holes through its top wall correlative to the openingsaforementioned and respectively receivable to the terminal prongs ofsaid electron tube, a similar plurality of correlative contact elementsof springy electrical conducting material secured to the interior ofsaid adaptor and disposed within the cavity aforesaid, a similarplurality of correlative terminal screws threaded through the lateralwall of said adaptor and adapted respectively to urge said contactelements inwardly into contact with said terminal prongs,

said terminal screws respectively extendin outwardly through theopenings aforesaid in the cup, and electrical connection means on theoutwardly extending portion of each of said terminal screws.

EDWARD R. HARRIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,004,610 Jones June 11, 19352,388,246 Berger Nov. 6, 1945

